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COBOL Tutorial

COBOL FUNCTION Keyword

The FUNCTION keyword represents a sophisticated built-in operation access mechanism within COBOL programming environments, serving as the primary gateway for utilizing intrinsic functions that provide comprehensive mathematical computations, string manipulation capabilities, date and time processing operations, and data conversion utilities. This keyword embodies the principles of modular programming by offering pre-built, tested, and optimized functionality that eliminates the need for custom implementation of common operations while ensuring consistent behavior across different COBOL implementations and maintaining high performance standards in enterprise applications that require reliable computational services and data processing capabilities.

Syntax and Usage

FUNCTION Keyword Syntax
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FUNCTION function-name
FUNCTION function-name(argument1)
FUNCTION function-name(argument1, argument2, ...)
 
*> Examples:
MOVE FUNCTION CURRENT-DATE TO WS-DATE
COMPUTE WS-RESULT = FUNCTION SQRT(WS-NUMBER)
MOVE FUNCTION UPPER-CASE(WS-STRING) TO WS-UPPER-STRING
Built-in Functions
Mathematical
String Processing

Common Intrinsic Functions

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IDENTIFICATION DIVISION.
PROGRAM-ID. FUNCTION-EXAMPLES.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01  NUMERIC-VALUES.
    05  WS-NUMBER-1         PIC 9(5)V99 VALUE 123.45.
    05  WS-NUMBER-2         PIC 9(5)V99 VALUE 678.90.
    05  WS-RESULT           PIC 9(7)V99.
    05  WS-INTEGER          PIC 9(5).
 
01  STRING-VALUES.
    05  WS-INPUT-STRING     PIC X(50) VALUE 'Hello World'.
    05  WS-UPPER-STRING     PIC X(50).
    05  WS-LOWER-STRING     PIC X(50).
    05  WS-STRING-LENGTH    PIC 9(3).
 
01  DATE-TIME-VALUES.
    05  WS-CURRENT-DATE     PIC X(21).
    05  WS-CURRENT-TIME     PIC X(8).
    05  WS-JULIAN-DATE      PIC 9(7).
 
PROCEDURE DIVISION.
MAIN-PROCESSING.
    *> Mathematical Functions
    COMPUTE WS-RESULT = FUNCTION MAX(WS-NUMBER-1, WS-NUMBER-2)
    DISPLAY 'Maximum value: ' WS-RESULT
    
    COMPUTE WS-RESULT = FUNCTION MIN(WS-NUMBER-1, WS-NUMBER-2)
    DISPLAY 'Minimum value: ' WS-RESULT
    
    COMPUTE WS-RESULT = FUNCTION SQRT(WS-NUMBER-1)
    DISPLAY 'Square root of ' WS-NUMBER-1 ': ' WS-RESULT
    
    COMPUTE WS-INTEGER = FUNCTION INTEGER(WS-NUMBER-1)
    DISPLAY 'Integer part of ' WS-NUMBER-1 ': ' WS-INTEGER
    
    COMPUTE WS-RESULT = FUNCTION ABS(-456.78)
    DISPLAY 'Absolute value: ' WS-RESULT
    
    *> String Functions
    MOVE FUNCTION UPPER-CASE(WS-INPUT-STRING) TO WS-UPPER-STRING
    DISPLAY 'Uppercase: ' WS-UPPER-STRING
    
    MOVE FUNCTION LOWER-CASE(WS-INPUT-STRING) TO WS-LOWER-STRING
    DISPLAY 'Lowercase: ' WS-LOWER-STRING
    
    COMPUTE WS-STRING-LENGTH = FUNCTION LENGTH(WS-INPUT-STRING)
    DISPLAY 'String length: ' WS-STRING-LENGTH
    
    *> Date and Time Functions
    MOVE FUNCTION CURRENT-DATE TO WS-CURRENT-DATE
    DISPLAY 'Current date: ' WS-CURRENT-DATE
    
    MOVE FUNCTION WHEN-COMPILED TO WS-CURRENT-TIME
    DISPLAY 'Compilation time: ' WS-CURRENT-TIME
    
    COMPUTE WS-JULIAN-DATE = FUNCTION DATE-OF-INTEGER(2024001)
    DISPLAY 'Julian date: ' WS-JULIAN-DATE
    
    STOP RUN.

Function Categories

Mathematical Functions
  • • ABS - Absolute value
  • • MAX - Maximum value
  • • MIN - Minimum value
  • • MOD - Modulo operation
  • • SQRT - Square root
  • • SIN, COS, TAN - Trigonometric
  • • LOG, LOG10 - Logarithms
  • • INTEGER - Integer part
String Functions
  • • UPPER-CASE - Convert to uppercase
  • • LOWER-CASE - Convert to lowercase
  • • LENGTH - String length
  • • REVERSE - Reverse string
  • • TRIM - Remove spaces
  • • CHAR - Character from code
  • • ORD - Character code
  • • NUMVAL - Numeric value

Interactive Tutorial

Hands-On Exercise: Function Applications
Practice using intrinsic functions for common programming tasks

Exercise 1: Data Validation

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01 INPUT-DATA.
   05 USER-INPUT PIC X(20).
   05 NUMERIC-VALUE PIC 9(8)V99.
   05 VALIDATION-RESULT PIC X(10).
 
PROCEDURE DIVISION.
    *> Validate and convert input
    IF FUNCTION TEST-NUMVAL(USER-INPUT) = 0
        COMPUTE NUMERIC-VALUE = FUNCTION NUMVAL(USER-INPUT)
        MOVE 'VALID' TO VALIDATION-RESULT
    ELSE
        MOVE 'INVALID' TO VALIDATION-RESULT
    END-IF
    
    *> Check range using MAX/MIN
    IF NUMERIC-VALUE = FUNCTION MAX(NUMERIC-VALUE, 1000)
       AND NUMERIC-VALUE = FUNCTION MIN(NUMERIC-VALUE, 9999)
        DISPLAY 'Value is within acceptable range'
    END-IF.

Exercise 2: Text Processing

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01 TEXT-PROCESSING.
   05 INPUT-TEXT PIC X(100).
   05 PROCESSED-TEXT PIC X(100).
   05 WORD-COUNT PIC 9(3) VALUE 0.
 
PROCEDURE DIVISION.
    *> Normalize text case
    MOVE FUNCTION UPPER-CASE(
        FUNCTION TRIM(INPUT-TEXT)) TO PROCESSED-TEXT
    
    *> Count words (simplified)
    PERFORM VARYING WS-INDEX FROM 1 BY 1
        UNTIL WS-INDEX > FUNCTION LENGTH(PROCESSED-TEXT)
        IF PROCESSED-TEXT(WS-INDEX:1) = SPACE
           AND PROCESSED-TEXT(WS-INDEX + 1:1) NOT = SPACE
            ADD 1 TO WORD-COUNT
        END-IF
    END-PERFORM.

Advanced Function Usage

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IDENTIFICATION DIVISION.
PROGRAM-ID. ADVANCED-FUNCTIONS.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01  STATISTICAL-DATA.
    05  VALUES-ARRAY OCCURS 10 TIMES PIC 9(5)V99.
    05  ARRAY-INDEX         PIC 9(2).
    05  TOTAL-SUM           PIC 9(7)V99.
    05  AVERAGE-VALUE       PIC 9(5)V99.
    05  VARIANCE            PIC 9(7)V99.
 
01  DATE-CALCULATIONS.
    05  START-DATE          PIC 9(8).
    05  END-DATE            PIC 9(8).
    05  DAYS-DIFFERENCE     PIC 9(5).
    05  BUSINESS-DAYS       PIC 9(5).
 
PROCEDURE DIVISION.
ADVANCED-PROCESSING.
    *> Statistical calculations using functions
    COMPUTE TOTAL-SUM = FUNCTION SUM(VALUES-ARRAY(ALL))
    COMPUTE AVERAGE-VALUE = TOTAL-SUM / 10
    
    *> Find maximum and minimum values
    DISPLAY 'Maximum value: ' FUNCTION MAX(VALUES-ARRAY(ALL))
    DISPLAY 'Minimum value: ' FUNCTION MIN(VALUES-ARRAY(ALL))
    
    *> Calculate variance
    PERFORM VARYING ARRAY-INDEX FROM 1 BY 1 UNTIL ARRAY-INDEX > 10
        COMPUTE VARIANCE = VARIANCE + 
            FUNCTION ABS(VALUES-ARRAY(ARRAY-INDEX) - AVERAGE-VALUE) ** 2
    END-PERFORM
    COMPUTE VARIANCE = VARIANCE / 10
    
    *> Date arithmetic
    MOVE FUNCTION CURRENT-DATE(1:8) TO START-DATE
    COMPUTE END-DATE = FUNCTION INTEGER-OF-DATE(
        FUNCTION DATE-OF-INTEGER(START-DATE) + 30)
    
    COMPUTE DAYS-DIFFERENCE = 
        FUNCTION INTEGER-OF-DATE(END-DATE) - 
        FUNCTION INTEGER-OF-DATE(START-DATE)
    
    DISPLAY 'Days between dates: ' DAYS-DIFFERENCE
    
    STOP RUN.

Best Practices

Knowledge Check

Test Your Understanding

Question 1: Function Syntax

What's the correct syntax to get the length of a string variable?

Answer: FUNCTION LENGTH(string-variable) returns the length of the string including trailing spaces.

Question 2: Mathematical Functions

How do you find the maximum value between three numbers?

Answer: FUNCTION MAX(number1, number2, number3) or use nested MAX functions: FUNCTION MAX(FUNCTION MAX(number1, number2), number3).

Question 3: Date Functions

What function provides the current system date and time?

Answer: FUNCTION CURRENT-DATE returns a 21-character string containing current date, time, and time zone information.

Common Patterns

Data Validation
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01 INPUT-VALIDATION.
   05 USER-INPUT PIC X(20).
   05 CLEAN-INPUT PIC X(20).
 
PROCEDURE DIVISION.
    *> Clean and validate input
    MOVE FUNCTION TRIM(
        FUNCTION UPPER-CASE(USER-INPUT)) TO CLEAN-INPUT
    
    IF FUNCTION TEST-NUMVAL(CLEAN-INPUT) = 0
        DISPLAY 'Valid numeric input'
    ELSE
        DISPLAY 'Invalid input'
    END-IF.
Statistical Analysis
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01 SALES-DATA OCCURS 12 TIMES PIC 9(7)V99.
01 STATISTICS.
   05 TOTAL-SALES PIC 9(9)V99.
   05 AVERAGE-SALES PIC 9(7)V99.
 
PROCEDURE DIVISION.
    COMPUTE TOTAL-SALES = FUNCTION SUM(SALES-DATA(ALL))
    COMPUTE AVERAGE-SALES = TOTAL-SALES / 12
    
    DISPLAY 'Highest month: ' FUNCTION MAX(SALES-DATA(ALL))
    DISPLAY 'Lowest month: ' FUNCTION MIN(SALES-DATA(ALL)).

Frequently Asked Questions

Related Concepts

Intrinsic Functions

Built-in COBOL functions and their applications

Mathematical Operations

COBOL mathematical computations and calculations

String Processing

Text manipulation and string handling functions